REPORT ON ZOOLOGY. 171 



sight into the method of variation of that organ, teaches us in 

 consequence its exact value, and when viewed in connexion with 

 other systems previously established upon other characters, may 

 serve to correct and perfect many details in these last beyond 

 what we might be able to do by anj'^ other method. With re- 

 ference to this end, besides the above, I may refer to a system 

 of Dr. Ritgen, in the Transactions of the Ceesarean Academy at 

 Bonn*, established upon the characters of the pelvis, as one, 

 not to be adopted entire, but capable perhaps of furnishing some 

 valuable hints which might otherwise be lostf. 



The external characters of birds have recently received much 

 attention from M. Isidore Geoffroy St. Hilaire, who has published 

 a memoir on this subject in the Nouv. Ann, du Miis.X which de- 

 serves to be consulted by all ornithologists. He has reviewed 

 those in most general use, and pointed out several of wliich he 

 thinks the proper value has not been correctly appreciated. He 

 particulai'ly mentions the emargination of the bill, so much 

 trusted to in characterizing the Dentirostres, as one to which too 

 much importance has been attached. On the other hand, he 

 regards the disposition of the toes, in the Passeres more parti- 

 cularly, as not having been sufficiently studied in a general point 

 of view. His researches indeed on this point have led him to 

 propose a new arrangement of the order just mentioned, which 

 he divides into the three groups of Zt/godactyles, SyndactyleSy 

 and Deodactyles, this last comprising the great bulk of the 

 genera, which have the toes divided in the regular way. Hence 

 it will be seen that he does not side with those who regard the 

 Scansores as forming a distinct order. The feet of the Passeres, 

 and the characters which they furnish, have likewise been much 

 attended to by M. Dela Fresnaye, who has also proposed a new 

 arrangement of this order §, though not exactly upon the same 

 plan as Geoffroy's. The year previously to that in which Isidore 

 Geoffroy published the above memoir, he gave some new obser- 

 vations in the ^?M«a/e5 rfe* 'S't?e«6'cs|| relating to the characters 

 of the Strigidce in particular, to which however it Avould occupy 

 too much room to alhide more particularly. 



The structure and mode of development of feathers, which has 

 been so ably illustrated by Fred. Cuvier*[[, and subsequently by 



* torn. xiv. p. 217. 



t The jielvis of birds has been recently studied bj' M. Bourjot St. Hilaire, 

 and made the subject of a memoir, read to the Royal Academy of Sciences at 

 Paris in August last. See Ulnstitut, No. 66, p. 266. J torn. i. p. 357. 



§ See an abstract of M. De la Fresnaye's memoir in the report of the French 

 Congress held at Caen in 1833, p. 69. Sec also other memoirs by him on the 

 same subject in Guerin's Magasiii de Zoologie for 1832 and 1833. 



Ij 1830i torn. xxi. p. li)l. ^ Mem. du Mus. 1825, torn. xiii. p. 327. 



